Motor learning leads to a multitude of neurological changes, including reduced energy consumption for the associated task (Picard et al. 2013), increased gray matter volume (Draganski et al. 2004) and changes in white matter (WM) organization (Scholz et al. 2009; Sampaio-Baptista et al. 2013). WM plasticity is of particular interest. Myelin, the fatty insulator of axons, allows for rapid and secure conduction of neural impulses. Structural changes in WM, particularly increases in myelination (as quantified by fractional anisotropy) and mean diffusivity (MD), are associated with the acquisition of new motor skills (Sampaio-Baptista et al 2013). Myelin is involved in learning, neurological disorders such as multiple sclerosis, and psychiatric disorders including depression and schizophrenia (Fields 2008). However, two key questions remain: 1) do changes in myelin underlie the WM plasticity observed with imaging? and 2) to what extent are functional connectivity networks strengthened after motor learning? The objective of the proposed research is to combine behavior, neuroimaging and histological assessments of brain structure and function to explore WM plasticity. Specifically, we will investigate the histological changes in WM hypothesized to be associated with changes in FA and MD as obtained via neuroimaging. We will also investigate changes in WM organization and reorganization of functional connectivity networks as a function of motor learning. The proposed research will provide fundamental knowledge concerning the dynamic nature of WM, and has relevancy to the field of motor learning and the field of motor rehabilitation after brain damage, such as stroke.